Recently, a hybrid maglev motor in a double bias permanent magnetic system has been proposed as a maglev motor.
A 5-axis-controlled hybrid magnetic bearing according to the patent document 1 realizes magnetic levitation and rotation on a long axis rotor for forming a pump impeller etc. by efficient 5-axis control using a permanent magnet for generating a bias magnetic flux. By devising a magnetic path of the bias magnetic flux, magnetic suspending force higher than that of a magnetic levitation system using only an electromagnet can be generated.
According to the patent document 2, a double bias magnetic bearing (magnetic suspension control) can generate further magnetic suspending force by providing a plurality of bias magnets for a conventional hybrid magnetic bearing. In addition, the flow of the magnetic flux of a secondary bias permanent magnet is induced by a primary bias permanent magnet, thereby realizing a more powerful hybrid magnetic bearing.
However, when the patent document 1 is applied to a pump etc., the projected poles for controlling the position in the axis direction on both end surfaces of a rotor complicate the structure of the inlet and the outlet of the pump, and causes difficult assembly. Furthermore, since the path of a liquid is complicated, intake and discharge losses increase. In addition, since the patent document 1 provides the magnetic bearings at the upper and lower portions of the rotor to suspend the rotor, it is difficult to generate a small hybrid maglev motor.
Additionally, since the patent document 2 has the structure of the projected poles arranged circularly on the magnetic bearing and having alternate polarity of N and S, an eddy current is generated when the rotor rotates, thereby increasing rotation losses of the rotor.    [Patent Document 1] Japanese Published Patent Application No. 2006-14528    [Patent Document 2] Japanese Published Patent Application No. 2007-120635